The four mechanical organs that form part of the collection at the Organ Theatre all operate from cardboard book music which is perforated with the information to control the organ's functions. These cardboard books contain all the playing notes and have additional perforations devoted to controlling the registers (stops), the tremulants and other perforations that operate the percussion instruments.

The fan-fold cardboard book is transported through a device termed a 'keyframe' that is mounted on the organ. The keyframe has a row of keys that are all held down by the cardboard.
The keys are sprung against the cardboard and will only lift into the perforations when they coincide. This then opens a valve and air is passed into the organ and to the corresponding mechanism which controls that function.